Volumetric ultrasound scanning of the breast has been proposed as a complementary modality for breast cancer screening as described, for example, in the commonly assigned US 2003/007598A1 published Jan. 9, 2003, which is incorporated by reference herein. The commonly assigned WO 2004/030523A2 published Apr. 15, 2004, which is incorporated by reference herein, describes a full-field breast ultrasound (FFBU) scanning apparatus that compresses a breast along planes such as the craniocaudal (CC) plane, the mediolateral oblique (MLO) plane, etc., and ultrasonically scans the breast. One side of an at least partially conformable, substantially taut membrane or film sheet compresses the breast. A transducer translation mechanism maintains an ultrasound transducer in contact with the other side of the film sheet while translating the ultrasound transducer thereacross to scan the breast.
Other FFBU scanning devices that compress the breast in other directions, such as in generally chestward or “head-on” directions, are described in one or more of the following commonly assigned applications, each of which is incorporated by reference herein: U.S. Ser. No. 60/565,698 filed Apr. 26, 2004; U.S. Ser. No. 60/577,078 filed Jun. 4, 2004; U.S. Ser. No. 60/629,007 filed Nov. 17, 2004; U.S. Ser. No. 60/702,202 filed Jul. 25, 2005; U.S. Ser. No. 60/713,322 filed Aug. 31, 2005; WO 2005/104729A2 published Nov. 10, 2005; and WO 2005/120357A1 published Dec. 22, 2005.
One inherent problem in chestward compression ultrasonic mammography scans is ultrasonic “shadowing” caused by the nipple onto the tissue behind the nipple. The nipple and areola have a higher tissue density and acoustic attenuation compared with the remaining breast tissue. In a chestward compression scan, the nipple and areola are directly in the path of the acoustic waves between the transducer elements and substantial portions of underlying breast tissue. Therefore, an acoustic “shadow” is cast onto the underlying breast tissue positioned directly behind the nipple area. This nipple shadow effect can make it more difficult to analyze the underlying tissues in the resultant mammographic images.
Nipple shadowing is often less of a problem for non-chestward ultrasonic imaging. For example, in the cranio-caudal scans and medio-lateral oblique scans, the nipple is often not in the pathway of substantial portions of other breast tissue. Examples of non-chestward ultrasonic mammography are WO 2006/035381 A1, and US 2003/0149364 A1.
Thus, it would be desirable to facilitate automated chestward ultrasound scanning of a breast tissue volume in a manner that alleviates or otherwise reduces the effects of nipple shadowing.